What do you call a baby wren?

Answer: chick

A baby wren is called a chick. The wrens are passerine birds in the mainly New World family Troglodytidae. There are about 80 species of true wrens in about 20 genera, though the name is also ascribed to other unrelated birds throughout the world. Only one species occurs in the Old World, where it is commonly known simply as the Wren; it is called Winter Wren in North America.